

import java.lang.reflect.Array;
import java.math.BigInteger;
import java.util.ArrayList;

public class jin {

	public static void main(String args[]) {
		int num = 100;
		System.out.println(Wayfour(num));
	}

	public static synchronized BigInteger Wayfour(int num) {
		ArrayList list = new ArrayList();
		list.add(BigInteger.valueOf(1));
		for (int i = list.size(); i <= num; i++) {
			BigInteger lastface = (BigInteger) list.get(i - 1);
			BigInteger lastfact = null;
			BigInteger nextface = lastfact.multiply(BigInteger.valueOf(i));
			list.add(nextface);
		}
		return (BigInteger) list.get(num);
	}
}